1. Field of the Invention
The present invention generally relates to a transfer and inoculation device useful for transferring, including storage for extended periods, of microorganisms to laboratory growth media. The present invention is particularly useful for testing the quality of a variety of laboratory growth media. More particularly, the present invention relates to a storable, inoculation device including one or more known, stabilized microorganisms and a method of producing, stabilizing and storing the same.
2. Description of the Background
Various culture media are routinely used in the growth of specimens in standard diagnostic procedures by laboratories engaged in providing microbiological analyses. A typical clinical laboratory employs a variety of different media types with each specimen submitted for examination. For example, a submitted specimen is often initially inoculated onto agar plates and, after an initial incubation, individual microorganism types are separated and identified using additional growth media. These methods are used routinely in making diagnostic predictions relating to many infections.
In performing these tests, the quality and state of the various culture media must be maintained. Further, clinical laboratories are required by various regulatory and certifying agencies to routinely subject samples of media to quality control evaluation. This testing must be performed on all culture media, whether the media is commercially purchased or is prepared by the facility. The frequency of testing varies from daily testing to random testing of individual lots.
For these quality control tests, appropriate microorganisms are cultured on the growth medium sample. After a prescribed inoculation period, often about 24 hours to 48 hours, at a prescribed temperature, generally about 35.degree. C., the growth patterns of the inoculated microorganisms are observed. These growth patterns may be observed merely qualitatively and the medium approved or disapproved based comparison to expected results. Alternatively, growth patterns may be studied more closely for quantitative analysis prior to approval of the medium.
The testing methods generally employed are conventional and known to those in the art. However, in summary, the microorganism to be used in the test is often cultured in a broth tube overnight. Microorganisms are transferred from the broth to the surface of the medium to be tested using a standard, sterile inoculation loop. For example, plastic disposable loops or reusable metal loops which have been heat-sterilized by flame or electric heating are generally employed. The inoculated media is incubated at a prescribed temperature, often 35.degree. C., for a prescribed time, generally about 24-48 hours. In a qualitative test, the microbial growth resulting from this procedure is simply observed and characterized as either typical or atypical. In quantitative testing, a known quantity of microorganisms prepared by dilution from the broth is placed in the medium to be tested by the above transfer procedure. After the prescribed incubation period, comparative culture counts are made.
These testing procedures require that the test microorganisms be viable and that the microorganisms maintain similar characteristics from generation to generation. Many laboratories maintain a supply of testing microorganisms by continually subculturing derived from the original microorganisms. However, this repeated subculturing is time-consuming and costly. But, more importantly, repeated subculturing often leads to the eventual loss of some of the original characteristics of the microorganism. Further, some microorganisms have relatively short lives and must repeatedly be subcultured, often once a day, presenting a drain on the resources and time of the laboratory. In summary, the subculturing of test microorganisms simply results in the unnecessary expenditure of laboratory resources and time, together with an increased chance for the production of mutated cultures.
Lyophilization and dessication techniques for preserving bacteria have been known for decades. In fact, a variety of strains of lyophilized bacteria useful for testing purposes are available commercially. These products generally comprise resealable storage bottles or vials containing small discs of gelatin and charcoal containing the desired bacteria. These discs are removed from the vial or storage bottles and used to directly or indirectly inoculate a growth medium or broth as described above.
The culturing and subculturing of inoculation microorganisms is undesirable for the reasons stated above. Further, the commercially available discs are difficult to handle, requiring aseptic manipulation by tweezers or tongs and the like.
The improved inoculation device of the present invention provides an easily manufactured, easily stored and easily manipulated device. Such a device contains one or more known, stabilized microorganisms for accurate and easy inoculation of growth media for testing purposes.